Platen for contour sanding, grinding and polishing



Nov. 8, 1966 H. w. CRETSINGER 3,283,447

PLATEN FOR CONTOUR SANDING, GRINDING AND POLISHING Filed March 19, 1964 5 Sheets-Sheet 1 HIRAM w. 2%?95'252 BY .QA W/ W ATTORNEYS N 1956 H. w. CRETSINGER 3,283,447

PLATEN FOR CONTOUR SANDING, GRINDING AND POLISHING Filed March 19, 1964 5 Sheets-Sheet 2 FKS. 4

FIG.5

INVENTOR. HIFZAM W. CRETSINGER BY W W a ATTORNEYS ,QWI

Nov. 8, 1966 H. w. CRETSINGER 3,283,447

PLATEN FOR CONTOUR SANDING, GRINDING AND POLISHING Filed March 19, 1964 5 Sheets-Sheet 3 FIG. 8

FIG. 9

PRESSURE REGULATOR PRESSURE PRESSURE REGULATOR 93 PRESSURE I N VENTOR. HIRAM W. CRETSINGER ATTORNEYS United States Patent 3,283,447 PLATEN FOR CONTOUR SANDING, GRINDmG AND POLISHING Hiram W. Cretsinger, 1401 S. 1st St., Redfield, S. Dak. Filed Mar. 19, 1964, Ser. No. 353,138 20 Claims. (Cl. 51-141) This application is a continuation-in-part of my copending application Serial No. 263,551, filed March 7, 1963, entitled Platen for Contour Sanding, Grinding and Polishing.

The present invention has relation to abrading machines and more particularly to a platen for use with a belt type abrading machine which will permitsanding, grinding or polishing work pieces with contours formed transversely to the direction of belt movement.

In the manufacture of wooden, metal or plastic items 7 having great length and being curved transversely, for example the seats for church pews, cabinets or wood, metal or synthetic parts, the bottleneck to efficient production has been in sanding, grinding and polishing the piece. While belt sanders, grinders and polishers can be used efficiently for abrading flat work smooth, the transverse curve of a pew seat and other elongated pieces has defied mechanization. The common method now is to use very narrow belt sanders and sand a small portion of the transversely curved seat at a time. A fixed solid platen is used for shaping the belt to a portion of the curve. However, there areno machines being made in which the entire width of the church pew seat can be sanded at once and in a continuous operation.

The device of the present invention in the form as disclosed, illustrates a belt sander which has a novel platen 'that permits the application of the sanding belt to the curved surface to be sanded under uniform pressure. This eliminates the objectionable variations in pressure on the work pieces that are normally encountered when a curved surface is to be sanded, using a standard or fixed platen. In the ordinary application, the high portions are sanded too much and the low areas are not touched.

Many factors determine the pressure that the sanding belt exerts on the work piece. Belt speed, variable belt tensions, both static and under movement, as well as the resilience of the platen used for pressing the belt into engagement with the work piece. The unique structure utilized in the platen of the present invention permits adjustments in pressure at any location across the face of the work .piece after the variables, such as speed and differential belt tensions are determined. The pressure can be adjusted While the machine is running.

A first form of the present invention, as shown, discloses a platen which can be utilized with a suitable abrading belt to finish transversely curved work pieces wherein the work piece has the same transverse configuration throughout its length. The platen is situated above the belt and work piece with its longitudinal axis extending transversely to the belt and work piece. The platen is laterally compressed in the portions thereof above the low points of the work piece. The platen will bulge in these laterally compressed portions and by supporting the platen with a flat plate on its upper side the bulges will protrude downwardly.

The bulges will force the belt into the depressions forming the transverse curve of the work piece, and, by proper adjustment of the lateral compression mechanism, the belt pressure will be kept uniform across the entire surface of the work piece.

Second and third forms of the invention illustrate platens which utilize quickly adjustable lateral support mechanism. The lateral support mechanisms of the second and third forms of the invention utilize fluid pressure which'operates on devices designed to squeeze the sides Patented Nov. 8, 1966 ice individual pressure regulators for each device the amount of lateral compression in different portions of the resilient member can be different. This will cause different amounts of downward bulge in different portions of the resilient member and in this manner a transverse curve can be sanded.

The description herein will deal with a sanding machine but it is to be understood that the invention will work on grinders and polishers for wood, metal, plastic and other materials. I

It is an object of the present invention to present a platen for an abrading machine which makes the machine usable for finishing transversely curved surfaces.

In the drawings,

FIG. 1 is a fragmentary perspective view of a belt type abrading machine having a platen made according to the present invention;

FIG. 2 is a sectional view taken as on line 22 in FIG. 1 and showing a platen used with the belt abrading machine in the present invention;

FIG. 3 is a bottom plan view of the platen of FIG. 2;

FIG. 4 is a top plan view of an insert member used in the platen shown in FIG. 3;

FIG. 5 is an end elevational View of the device of FIG. 2 as viewed from the left end thereof;

FIG. 6 is an end elevational view of the device of FIG. 2 as viewed from a right end thereof;

1 FIG. 7 is 'a side elevational view of the platen assembly of FIG. 2, with parts removed for clarity;

FIG. 8 is a side elevational view of a platen illustrating the lateral compression members made according to a second form of the invention with parts in section and parts broken away;

FIG. 9 is a sectional view taken as on line 9-9 in FIG. 8;

FIG. 10 is a fragmentary sectional view taken as on line 1010 in FIG. 9;

FIG. 11 is a fragmentary side elevational view of a third form of mechanism utilized for lateral compression on the platen of the present invention;

FIG. 12 is :a sectional view taken as on line 1212 in FIG. 10; and

FIG. 13 is a fragmentary sectional view illustrating the connection of piston rods to rocker arms in the third form of the invention.

Referring to the first form of the invention illustrated in FIGS. 1-7, and the numerals of reference thereon, a belt type abrading machine (belt sander) illustrated generally at 10 is mounted on a base 11 and has a work support table 12 vertically adjustably mounted thereon. An endless work conveyor or feed belt 13 is mounted over a pair of rollers 14, 14 rotatably mounted on the ends of the work support table. The endless conveyor belt is used to feed the work to be sanded into the belt sander. The conveyor belt is driven through a chain and sprocket arrangement that is powered from a conventional electric motor so that the upper surface of the belt is driven in direction as indicated by arrow 15.

The drive roller for the conveyor belt is in many cases driven through a variable speed drive of usual or preferred construction.

The work support table is positioned immediately below a belt sander drive assembly 16 that is also fixedly mounted with respect to base 11. The belt sander drive assembly includes a pair of side frame members 17, 17. The side frame members 17, 17 rotatably support a drive roller 20 (which, as shown, is driven from a conventional electric motor through suitable chain and sprockets), an idler roller 21 and an oscillation roller 22. The idler roller 21 is spaced in longitudinal direction with respect 11 to the conveyor belt 13 from the drive roller 20. The

joscillation roller 22 is positioned above the idler roller 21. An endless sanding belt 23 is mounted over the i drive roller, idler roller and oscillation roller and is driven by the drive roller in direction as indicated by arrow 24. y A support housing 25 is attached to the base 11 and v supports the side frame members 17, 17. The support housing has a hinged portion 26 which can be raised and lowered to cover the oscillation and idler rollers. The mounting of the oscillation roller is designed so that the axis of rotation thereof can be changed in angle in .order to cause the sanding belt 23 to move back and forth in longitudinal direction on the oscillation roller, as indicated by double arrow 27. This oscillation device can be any usual or preferred construction, typically it jWill involve mechanism for changing the position of one end of the roller shaft with respect to the other. I For example, as shown in FIG. 1, one end of the shaft 18 of the oscillation roller 22 can be rotatably mounted in a bearing block 19 that in turn is mounted on the end of a piston rod 28 for a short stroke air cylinder 29. .The roller is set so the belt tension at one edge is greater than at the other. This causes the belt to move axially along the rollers toward the edge with least tension. .With the piston rod 28 extended, the roller is positioned so that the belt moves away from the cylinder 29. When ;the belt reaches the far edge of the roller, suitable sensing .mechanism is activated and air is directed to cylinder 29 so that the rod 28 retracts. This will decreasethe tenision in the sanding belt adjacent the air. cylinder and 1 cause the belt to move toward the air cylinder. t When the belt has moved to its limit toward the air cylinder other sensing and control mechanism directs air to cylinder 28 so as to cause the rod 28 to extend once again. This restores the tension in belt 23 on the air 1 cylinder edge of the belt. The belt will once again move away from air cylinder 29 along roller 22.

In this manner the belt is moved back and forth in jorder to eliminate any irregularities in sanding on the f work piece and give a smooth finished job to the sanding. iThe main portions of the sanding machine just described are conventionally used for sanding fiat work at the present time with the exception that the drive roller and .the idler roller 21 are spaced farther apart than in a 3 conventional machine. i A platen assembly illustrated generally at 30 is posijtioned within the sanding belt substantially midway between the idler roller 21 and the drive roller 20 and bears against the inner surface of a bottom portion of the sandjing belt 23. The platen assembly 30 is designed so that a transversely curved work piece, for example a ?church pew seat 35, will be sanded at a uniform pressure along its top surface. The pew seat 35 will be moved by conveyorbelt 13 in direction as indicated by arrow 15.

The platen is mounted on brackets 31 which can be j released so that the platen can be removed from the drive assembly. The brackets releasably mount a top support ;plate 32. A pair of depending brackets 33, 33 are 'fixedly attached to the top support plate and they in turn are fixedly attached to a base plate 34.

i The platen base plate 34 has a pair of spaced, integral walls 36, 36 depending therefrom. The bottom edges of the walls are curved to be substantially identical to curvature of pew seat 35 but are spaced upwardly from the (sanding belt.

I The platen base plate 34 rigidly supports and backs up a deformable resilient member 37. As shown, the lresilient member 37 is an air filled inflatable tubular member 37. The resilient member 37 is attached to the .base plate with suitable clamps 38 and 39 which are fastened at opposite sides of the base plate with suitable cap screws. The member 37 is positioned between the spaced walls 36, 36. The inflatable or air filled resilient 4 member 37 is plugged at its ends with suitable hard plugs and 39, respectively, clamp onto the base plate 34. The.

wedge members 42 are used to insure that a tight seal is obtained between the resilient member 37 and the end plugs. The plugs back up the member so that the clamps securely seal the member 37 on the plugs and, in turn, the clamps securely attach it to the platen base plate. The resilient member 37 is preferably made of rubber or other air tight tubing having a tough canvas or other substantially non-stretchable cover. For example, in operation, a three inch fire hose has been found to be suitable. The member 37, must have resiliency so a hard outer cover is not satisfactory.

The resilientmember has, as shown, an integral rigid backbone or support 43 mounted therein. The backbone 43 is fixedly attached to the end plugs 40 and 41 and extends therebetween. As perhaps best seen in FIG. 4 the backbone or support 43 has the outer side edges thereof curved in a predetermined manner, depending on i the cross section of the work piece that is being sanded. As shown, the backbone support 43 has each edge curved to identically represent the curvature of the pew seat 35. As shown in dotted lines at 46 the outer edges of backbone 43 are formed by placing patterns taken from the cross section of the pew seats being sanded back to backand cutting the outer edges of support 43 to conform to the curvature of the seats.

The resilient member 37 isinflated to a predetermined pressure through a valve fitting 47 which is 'mounted on the base plate 34 and is open through a passageway. 48

provided in block 41 into the interior of the resilient member. The member can be inflated to any desired or necessary pressure, as will be more fully explained later.

The member also couldbe a pre-sealed air bag if the desired pressure was supplied prior to scaling.

The outer surface of the air filled resilient member,.at

the bottom thereof, forms the contour that the belt 23.

of the belt sander is to follow. In order to eliminate wear directly on the member 37 a strip of lubricated or anti-friction cloth 49 is placed between the member 37] and the inner surface of the sanding belt 23.. Thecloth 49 is attached to one of the side walls 36 of the platen assembly.

As can perhaps best be seen in FIG. 2 the bottom surface ofthe tubular air filled resilient member '37 forces the belt 23 to the proper configuration to sand the surfaces of the pew seat. In order to provide for thenecessary curves in the-surface of-the member 37, some portions of the resilient air filled member must be forced.

downwardly more than other portions. The resilient member 37 is, as shown, shaped by the curved inner surface of side wall 36, 36. The walls 36, 36 substantially match the curves of backbone 43, as seen in FIGS. 3

and 4.

The walls are shaped so that certain portions of the resilient member are forced inwardly, for example, portions 53 and 54. This corresponds with the areas where the backing support is narrow. The air filled member 37 is forced downwardly by these same portions, thus causing are thick and again cause the resilient member to bulge downwardly.

The final adjustment of the resilient member 37 is made by turning screws 52 against flexible strips 50, 50

which bear directly on opposite sides of the resilient member. By turning screw 52 inwardly or outwardly, the curvature of the bottom edge of the resilient member is accurately controlled.

The backbone or support 43 holds the top of the resilient member to a definite shape and prevents the member from bulging in the wrong places. The backbone, as shown, determines the extent that the resilient member can be deformed and insures that the downward bulge in the areas where the walls 36, 36 extend inwardly will be along a definite predetermined curve. Also the base plate prevents the upper side of the member 37 from bulging upwardly.

It should be noted that if desired the walls 36, 36 can be of uniform thickness and the forming of resilient air filled member 37 can be accomplished through the use of adjustment screws 52 and flexible strips 50, 50 only.

The resilient member 37 is flexible but still has a certain amount of body to it so that the performing of the resilient member causes it to conform substantially to the curvature of the pew seat. As shown, at this time the resilient member is still uninflated and is not sufficiently rigid or hard to be usable.

The resilient member 37 is then inflated to the desired pressure in order to give the necessary firmness to the platen and exert suflicient force on the sanding belt 23. In the areas where the member is bulged down the belt contacts the thin portions of the pew seat with a force equal to that at the high areas 55. The amount of downward force in the different areas can be controlled through the adjustment screws 52 as desired. The final adjustment of screws 52 can be made with the machine running so that the variable forces are allcompensated for at the final adjustment. The amount of air pressure necessary in resilient member 37 depends on the centrifugal force acting on the sanding belt, the friction between the belt and the work piece and the speed of the belt, as well as the hardness of the wood being sanded.

In the sanding of a pew seat, for example, it has been found that it is extremely difficult to keep the belt doing the sanding from wearing off the relatively sharp rear upper corner portion 60. The corner portion 60 is important because this is where the back piece fits onto the pew seat and if it is rounded off the fit is poor and the resulting product looks inferior.

In order to relieve the pressure of the sanding belt on corner 60 suificiently so that it can be sanded to a sharp point and not worn round by the belt, an auxiliary presser foot 61 is utilized. The pressure foot has a curved main portion 62 and a base portion 63. A neck 64 extends from the base portion and has rounded pivotal surfaces thereon. The neck 64 extends through a provided opening 65 in end clamp 39. The rounded surfaces of neck 64 pivot on the edge surfaces of this opening. An adjustment screw 66 is threadably mounted through an outwardly extending end of the neck portion 64 and engages a shoulder 67 on the end clamp 39. When the adjusting screw 66 is threaded inwardly against the shoulder 67 the presser foot will pivot in direction as indicated by arrow 70 so that the curved portion 66 is pressed against the bottom surface of the resilient member 37. This lifts the bottom surface of the member away from the corner 60 and the pressure against the corner is relieved. The sanding belt does not wear away the corner or round it off.

By adjustng the screws 52 to force the flexible strips against the resilient member to control its shape and adjusting the presser foot 61, a uniform pressure between the pew seat to be sanded and the sanding belt can be easily achieved. Also, the air pressure within the resilient inflatable member 37 can be regulated to obtain the desired firmness of the platen.

When small variations in structure are sanded the adjusting screws can move to make the necessary adjustments. However, if a substantially different curvature seal.

6. is to be sanded, a new backbone or support 43 should be inserted within the resilient inflatable member and the side walls 36, 36 shaped to conform to the new curvature.

the platen will force the belt down against the pew seats with the correct pressure for obtaining a good sanding job. No longer are the high areas, such as 55, sanded flat and the low areas such as 71 left untouched. The pressure across the entire width of the pew seat is even and the sanding job is uniform.

If desired, an auxiliary roller can be positioned against the sanding belt adjacent the forward end of the pew seat in order to obtain a little more sanding around the curve at the front of the pew seat.

The angle of incidence .between the belt 23 and the work piece is very small. The drive roller 20 and the idler roller 21 are nearly on a plane and the platen bottom surface is very little below the bottom edges of these two rollers. The distance between the 'drive and idler rollers is relatively large and thus the belt has sufficient space in which to conform to the configuration of the platen and no problem results from excessive wear or stretching of the belt. The oscillation of the belt back and forth as indicated by double arrow 27 does not affect operation of the platen.

Referring specifically to FIGS. 8, 9 and 10 and the second embodiment of the lateral support means for the platen of the present invention, it can be seen that a platen assembly is mounted onto the top support plate 32 through the use of depending brackets 33, 33 in the previous form of the invention. A platen base plate 81, which corresponds to base plate 34, is fixedly attached to the brackets 33, 33. The top support plate 32 can he supported in the machine as shown in FIG. 1. The platen base plate has a pair of spaced apart, integral walls 82,

82 depending therefrom. The bottom edges of the walls 82, 82 are curved to be substantially identical to the curvature of the pew seat or work piece on which they are working. The walls are spaced upwardly from the sanding belt as in the previous forms of the invention. A deformable resilient member 83 is mounted between the walls 82, 82 and below the platen base plate 81. The platen base plate 81 backs up and rigidly supports the resilient member 83, which as shown is a tubular air filled or inflatable member. The member 82 can be substantially identical in construction to the. deformable resilient member 37 shown in the first form of the invention.

As in the first form of the invention the resilient member 83 is held to the base plate with suitable clamps 38 and 39, which are fastened to the base plate with cap screws, as in the first form of the invention. The ends of the resilient member 83 are plugged with plugs 40 and 41. The wedge members 42 are used in the same manner as in the first form of the invention to effect a tight The plugs 40 and 41 back up the member 83 and the clamps securely seal the member on the plugs and in turn securely attach it to the platen base plate.

The resilient member 83 as shown, can be made of rubber or other air tight tubing having a tough canvas cover, for example, a three inch fire hose.

The backbone 43 is also fastened to the plugs 40 and 41 and clamps the upper wall of the resilient member 83 against the base plate 81.

In place of utilizing the side walls on the platen support member which conform to the curvature of the backbone member, as in the first form of the invention, and the screw adjustment, the side walls 82, 82 are of substantially uniform thickness throughout their length. In order to provide adjustable lateral support for the resilient deformable member 83, a plurality of resilient fluid filled bag members 85 are positioned along the side edges of the deformable member and fit between the in- In operation the conveyor belt 13 will carry the pew seats 35 forwardly underneath the sanding belt 23 and ner surfaces of theside walls 82, 82 and the deformable member. spaced closely adjacent one another and vary in vertical 1 length, depending on the amount of downward protrusion of the deformable member 83. The bags are positioned in transversely aligned pairs on opposite sides of the dei; formable member. ing each transverse pair on opposite sides of the deform- 5 able member are open to each other through a separate 1 tube 84. Each of the tubes is positioned within one of i a plurality of recesses 86 formed into the platen base 1 plate 81. A valve member 87 of any usual or preferred As can be seen in FIG. 8, the bags 85 are The interior of the two bags formdesign is provided in one bag of each pair of bags 85.

1 This provides a means for inflating the bags. The valve j members 87 for each pair of bags passes through provided openings 88 in the adjacent side wall 82 of the platen support member.

The valve member 87 is connected through a suitable conduct 91 to a pressure regulator 92 which in turn receives fluid under pressure from a source 93. The pressure source can be compressed air or other gas or, could be hydraulic fluid.

The pressure regulator is of any usual or preferred design which can be adjusted so that a known, set pressure 9 can be supplied to the interiors of the bags 85, 85. It will be noted that the pressure in the two bags of each pair will be equalized because of a tube 84 which opens to the I interiors of the bags 85. Each pair of bags is connected to a separate pressure regulator.

The bags will be tightly packed together, as can be seen in FIG. 8, and, if necessary, suitable small'projection or fins (shown in dotted lines in FIG. can be provided on the inner surfaces of the walls 82 to form j individual segments or compartments for the bags and prevent the bags from expanding greatly'in directions as 1 indicated by double arrow 94.

The bags are made of material which will stretch in directions as indicated by double arrow 95. The bags will 1 be inflated until they expand a sufiicient distance in direcr tions as indicated by arrow 95 so that the lateral pressure 1 on the resilient member 83 will be suflicient to cause it to bulge downwardly to match the contour of the piece being I sanded. This adjustment-is made by adjusting the pressure regulators'so that the desired pressure is maintained on each pair of bags 85, 85. Thus the amount of lateral j' pressure or squeeze at any place along the resilient member can be varied. Consequently a greater or lesser amount of downward bulge of the resilient member in substantially the same section of the platen can be obtained.

Theamount of lateral pressure can be very quickly adjusted in order to accommodate work pieces having a slightly diflerent transverse curve,if desired. Also the contour can be accurately adjusted.

It should be noted that FIGS. 8 and 9 omit the sanding belt and the anti-friction cloth 49 for the sake of clarity. These would be postioned as shown in FIG. 2 in relation to the platen.

The resilient member 83 can be inflated through the valve member 47 as explained in connection with the first form of the invention. The presser foot 61 can be adjusted in order to prevent excessive sanding of the corner 1 portion 60 of a pew seat, as previously explained.

It is therefore seen that by increasing the pressure in each pair of bags 85 so that they will expand in directions 1 as indicated by a double arrow 95 the amount of lateral compression or force on the resilient member 83 is increased, thereby increasing the downward bulge of the resilient member in substantially the same portions. The

. resilient member will be forced to bulge downwardly be- 8 constructed substantially identical to the previous forms of the invention. The platen assembly is mounted onto the top support plate 32 which has depending brackets 33 that mount a platen base plate 101. The base plate 101 v is utilized for supporting and mounting a resilient member 102 which is substantially identical in construction to the resilient members 37 and 83. The resilient member 102 is held in place with the clamps 38 and 39 as previously explained. The end plugs 40 and 41 and the means for inflating the resilient member 102 are the same. In addition, the backbone member 43 is positioned within the regularly spaced along the length of the resilient member- 102, or, in other words, extend in direction transverse to the direction of movement of the pew seat or curved work piece being sanded.

As many pairs of foot members 105 as is necessary to accomplish the desired compression of the resilient members can be used. The foot members 105 can be of greater vertical height where the resilient members bulge downwardly more. The feet 105, 105 are pivotally mounted as at 106, 106 (see FIG. 12) onto rods 107, 107.

The rods in turn are pivotally mounted at 108 to the lower portions of rocker arms 111, 111. The rocker arms 111,.

111 forming each opposed pair are positioned on opposite ones of the walls 103, 103. The rods 107, 107 can be adjusted in longitudinal direction with respect to the rocker arms 111, 111 by providing a plurality of pivot holes for fastening the rods to the rocker arms.

The rocker arms 107, 107 are each pivotally mounted as at 112, to a separate pair of ears 113, 113 which are in turn fixed to side walls 103, 103 adjacent the top portions thereof. The upper portions 114, 114 extend above the base plate 101.

A separate cylinder assembly 115 is fixedly attached to base plate 110, and aligned with each of the opposed pairs of rocker arms 111, 111. As can be'seen in FIG. 12 cylinder assembly has two internal slidably mounted piston members 116, 116 which in turn have attached rods 117, 117 extending outwardly from opposite ends of the cylinder assembly and each engaging the.

upper portions 114, 114of-one of the rocker arms 111, 111. The rods 117, 117 can be attached to the rocker arms 111, 111 through ball joints 120 or other suitable connection means. The ball joints 120 will permit the rocker arms to pivot about 112 within its intended range of movement without causing undue stress in the piston rods 117, 117.

A separate conduct 121, is open to the center portion 7 of each of the cylinder assemblies and opens at position between the pistons 116, 116. Each of the conducts 121. is open to a separate pressure regulator illustrated schematically and typically at 112, which in turn is open to a suitable source of fluid under pressure 123..

The fluid under pressure could be either air or hydraulic fluid and the pressure regulator 122 would be designe to accommodate the particular fluid used.

Thus, by admitting fluid under regulated pressure to the intenior of cylinder assembly 115 so that the pressure acts against the pistons 116, 116 it will be seen that the rods 117, 117 will bear against the upper portions of the rocker arms 111, 111 and move the rocker arms about their pivots 112, 112. This in turn will exert a force. through rods 107, 107 against the foot members 105, 105

whichv will then tend to laterally compress the resilient member 102, causing a downward bulge of the resilient member in substantially the same portion. If a greater bulge is desired more pressure is supplied by adjusting the pressure regulator and thereby exerting more pressure on the pistons 116, 116 and further squeezing :down the sides of the resilient member through the associated foot members 105, 105.

Inasmuch as the cylinder assembly 115, 115 are single acting, the resilient force of member 102 will move the foot members outwardly when the pressure in the cylinder is reduced. Also, the ball joints 120 will not become disengaged in the normal usage because the joints will always be under slight compressive force. Again, with this form of the invention the adjusting of the lateral support means for the resilient member 102 is greatly simplified and made much quicker acting than use of the screws illustrated in the first [form of the invention. The cylinder can be individually adjusted so that the downward bulge can be adjusted at different positions along the platen.

It is to be understood that the other details of construction of the platen is substantially the same a that shown in the first form of the invention including the clamps for holding the resilient member in place and utilization of the presser foot. The platen assembly 100 will fit into the sanding machine as the other platens will and the sanding belt will conform to the bottom surface of the resilient member 102 thus giving accurate transversely contoured sanding.

The sanding belt 23 will be operated as previously explained, and will be oscillated back and forth during operation. The adjustment of the compression devices shown in the second and third forms of the invention can be accomplished while the machine is working so that accurate settings compensating for all variables can be made.

It is now possible to have a belt sander, grinder or polisher which will sand transversely curved surfaces in a continuous operation without having a plurality of individual operations on the' various portions of the curved member or using hand machines.

The example illustrates the invention as used with a belt sanding machine for making wooden pew seats. The platen can be used with any belt type abrasion machine wherein transversely curved work pieces are to be shaped or abraded. Grindingof metal parts can be done as well as polishing or bufl'ing. All of these applications are intended to be within the concept of the invention.

What is claimed is:

1. A platen for holding an abrading member in engagement with a curved work piece movable relative to the abrading member, said platen comprising:

a frame,

a base plate,

means to mount said base plate on said frame,

an inflatable member mounted on said base plate and positioned to exert pressure on the surface of said abrading member opposite said work piece,

lateral support means on the sides of said inflatable member to reduce the width of said member in certain portions and increase the heighth thereof in the same portions, and

means to permit gas under pressure to be introduced in said inflatable member.

2. The combination as specified in claim 1 and a backbone member within said inflatable member, said backbone member having the edge surfaces thereof curbed to correspond to the surface of the work piece being abraded.

3. The combination as specified in claim 2 wherein said lateral support means for said inflatable member is comprised as a flexible strip positioned on each side of said inflatable member and a plurality of adjusting screws threadably mounted with respect to the base of said platen and adapted to engage said flexible strips and force them against said inflatable member.

4. The combination with an abrading machine having a work support table, means on said table to permit a work piece having a transversely curved upper surface to be moved longitudinally therealong, and a power driven endless abrading belt mounted over a pair of spaced substantially coplanar rollers positioned above and spaced from said support table, of: a platen to hold said abrading belt in engagement with a transversely curved work piece being moved longitudinally along said work support table, said platen comprising:

a platen base plate mounted on said abrading machine,

a tubular inflated member having a substantially nonstretchable cover mounted on said base plate and positioned to engage the inner surface of said belt, and

side support members fixed to said base plate and positioned onopposite sides of said inflated member and having means thereon to reduce the width of said inflated member in certain portions thereof and increase the heighth thereof in substantially the same portions, said inflated member being positioned to urge said belt against said transversely curved work piece with a uniform pressure across the upper surface thereof.

5. The combination as specified in claim 4 wherein said work piece is an elongated transversely curved seat having a sharp edge portion at one side thereof, and a presser foot, means to pivotally mount said presser foot on said base plate, adjustment means on said presser foot, said adjustment means being positioned so that the presser foot can be moved to exert pressure on said inflated member and lift said inflated member away from said sharp corner portion of said seat.

6. The combination as specified in claim 4 and a backbone member within said tubular inflated member, said backbone member having edge surfaces thereof curved to correspond to the upper surface of said work piece and being of size corresponding to the cross section of two curved work pieces placed back to back.

7. The combination with an abrading machine having a work support table, means on said table to permit a work piece having a transversely curved upper surface to be moved longitudinally therealong, and a power driven endless abrading belt mounted over a pair of spaced rollers positioned above and spaced from said support table, of:

a platen assembly mounted on said abrading machine within said belt and adapted to engage the inner surface of the lower portion of said belt and to force it into engagement with a transversely curved Work piece being abraded, said platen comprising:

a support member comprising a base plate having a pair of fixed downwardly depending walls,

an air tight tubular member made of resilient substantially non-stretchable material filled to a predetermined pressure,

a backbone support mounted inside said tubular member,

means for fastening said backbone support and said tubtlllar member to said base plate between said wal s,

a pair of longitudinally extending flexible members positioned between said tubular member and the adjacent wall of said base plate, and

means for forcing said flexible members inwardly against said tubular member.

8. The combination with an abrading machine having a work support table, means on said table to permit a work piece having a transversely curved upper surface to be moved longitudinally therealong, and a power driven endless abrading belt mounted over a pair of spaced rollers positioned above and spaced from said support table, of: a platen assembly mounted on said abrading machine within said belt and adapted to engage the inner surface of the lower portion of said belt and 11 V to force it into engagement with a transversely curved work piece being abraded, said platen comprising:

a support member comprising a base plate having a pair of fixed downwardly depending 'walls,

a resilient tubular member,

a backbone support mounted inside said tubular member,

means for fastening said ba'ckbone support and said tubular member to said base plate between said walls, and

adjustable lateral support means positioned to exert a lateral force between the depending walls of said base plate and the corresponding side wall of said tubular member, said tubular member being of sufficient resiliency to bulge downwardly in substantially the same sections as the section to which lateral force is applied and in proportion to the amount of a the lateral force.

9. The combination as specified in claim 8 wherein 1 the lateral support means are comprised as a plurality of oppositely disposed pairs of members supported by the depending walls of the platen assembly, each pair of 1 members being individually actuatable with fluid under pressure to bear against the sides of said resilient membet with a force proportional to the fluid pressure applied to the members.

10. The combination as specified in claim 8 wherein 1 the lateral support means is comprised as a plurality of transversely aligned pairs of resilient bags, .the bags forming each pair being open to each other, and separate means to introduce fluid under pressure to each pair of bags.

11. The combination as specified in claim 8 wherein the lateral support means includes a plurality of foot members arranged in transversely aligned pairs, said foot 12. The combination with an abrading machine having a support member comprising a base plate having a pair of fixed downwardly depending walls,

a resilient member engaging the abrading member,

a backbone support mounted at the side of said resilient member opposite the side thereof that engages the abrading member,

means for fastening said backbone support and said resilient member to said, base plate between said walls, the lateral edges of said backbone support being shaped to correspond to the curve of the work piece being abraded, and

adjustable lateral support means positioned to exert a lateral force between each of the depending walls of said base plate and the corresponding side wall of said resilient member, said resilient member being of sufiicient resiliency to bulge in direction against the abrading member in substantially the same sections as the section to which lateral force is applied and in proportion to the amount of the lateral force.

13. A platen for holding a moving belt type abrading member in engagement with a work piece engaging a surface of the abrading member, said platen comprising:

section shape of the abraded surface of the work piece.

14. The combination as specified in claim 13 and a presser foot mounted on said frame adjacent one end of said resilient deformable member, and means to adjust said presser foot so it can be moved to exert a force on said resilient member in direction away from said abrading member at position substantially aligned with one.

edge of the work piece.

15. A platen for holding a trasnversely flexible abrading member in engagement with a curved work piece engaging a surface of the abrading member, said platen comprising:

frame, resilient deformable member mounted on said frame and positioned to exert abrading pressure on the surface of said abrading member opposite said work piece,

backbone member supporting said resilient deformable member, said backbone member having the edge surfaces thereof curved to correspond to the surface of the Work piece being abraded, and

lateral support means on the frame and engaging the 16. A platen for holding a transversely flexible abrad-' a plurality of adjusting screws threadably mounted.

on the frame adapted to engage said flexible strips and force them against said resilient member.

ing member. in engagement with a curved work piece engaging a surfaceof the abrading member, said platen comprising:

a frame,

resilient deformable member mounted on said frame and positioned to exert abrading pressure on the surface of said abrading member. oppositev said work piece, and

lateral support means on the frame and engaging the sides of said resilient member to reduce the width of said member in certainportions and increase the height thereof in substantially the same portions, said lateral support means comprising a plurality of oppositely disposed pairs of support members supported by the frame, each pair of support members being individually actuable with fluid under pressure to bear against the sides of said resilient member .with a force proportional to the pressure applied to the support members.

' 17. A platen for holding a transversely flexible abrading member in engagement with a curved work piece engaging a surface of the abrading member, said platen comprising:

a resilient deformable member mounted on said frame a frame,

and positioned'to exert abrading pressure on the surface =of said abrading member opposite said work piece, and

lateral support means on the frame and engaging the transversely aligned pairs of resilient bags, the bags forming each pair being open to each other, and separate means to introduce fluid under pressure to each pair of bags. 18. A platen for holding a transversely flexible abrading member in engagement with a curved work piece engaging a surface of the abrading member, said platen comprising a frame,

a resilient deformable member mounted on said frame and positioned to exert abrading pressure on the surface of said abrading member opposite said work piece,

lateral support means on the frame and engaging the sides of said resilient member to reduce the width of said member in certain portions and increase the height thereof in substantially the same portion, wherein the lateral support means includes a plurality of foot members arranged in transversely aligned pairs, said foot members being transversely slidably mounted on the frame, a plurality of separate rocker arms pivotally mounted on the frame, each rocker arm being aligned with and connected to control one foot member, separate cylinder means for simultaneously actuating the rocker arms controlling the two foot members forming each transversely aligned pair, and means to selectively introduce fluid under pressure to the separate cylinder means.

119. The combination with an abrading machine having a work support table, means on said table to permit a work piece having a transversely curved upper surface to be moved longitudinally there-along, and a power driven endless abrading belt mounted over a pair of spaced rollers positioned above and spaced from said support table, of:

a platen assembly mounted on said ab-rading machine within said belt, said platen comprising:

a frame,

a resilient member mounted on said frame on a side of said abrading belt opposite from the transversely curved surface of the work piece and positioned to exert pressure onto said abrading member to engage the abrading member with the curved surface, and

lateral support means positioned along the sides of said resilient member, said lateral support means compressing said resilient member in direction substantially parallel to the direction of motion of the Work piece in at least two transversely spaced portions on the same side thereof to increase the height of the resilient member and cause a bulge towards the abrading member in substantially the same portions, the general profile of said resilient member on at least one side thereof, as supported by said lateral support means substantially corresponding to the cross sectional configuration of the transversely curved surface of the work piece.

20. The combination with an abrading machine having a work support table, means on said table to permit a work piece having a transversely curved upper surface to be moved longitudinally thereailong, and a power driven endless abrading belt mounted over a pair of spaced rollers positioned above and spaced from said support table, of:

a platen assembly mounted on said abr-ading machine said belt and adapted to engage the inner surface of the lower portion of said belt and to force it into engagement with a transversely curved work piece being abraded, said platen comprising:

a frame,

a resilient deformable member mounted on said frame 25 :in position to exert pressure across the width of said belt, and

lateral support means on the frame and engaging the sides of said resilient deformable member to reduce the width of said member in certain portions and increase the height thereof in substantially the same portions, thereby increasing the distance of said belt away from a reference plane in those portions, said lateral support means being adjusted so that the increase in height of the resilient deformable member from its normal position substantially corresponds to the amount that the curved surface of the work piece is depressed from its high points with respect tothe reference plane.

References Cited by the Examiner UNITED STATES PATENTS 1/1949 Stag-gs 51-375 

1. A PLATEN FOR HOLDING AN ABRADING MEMBER IN ENGAGEMENT WITH A CURVED WORK PIECE MOVABLE RELATIVE TO THE ABRADING MEMBER, SAID PLATEN COMPRISING: A FRAME, A BASE PLATE, MEANS TO MOUNT SAID BASE PLATE ON SAID FRAME, AN INFLATABLE MEMBER MOUNTED ON SAID BASE PLATE AND POSITIONED TO EXERT PRESSURE ON THE SURFACE OF SAID ABRADING MEMBER OPPOSITE SAID WORK PIECE, LATERAL SUPPORT MEANS ON THE SIDES OF SAID INFLATABLE MEMBER TO REDUCE THE WIDTH OF SAID MEMBER IN CERTAIN PORTIONS AND INCREASE THE HEIGHT THEREOF IN THE SAME PORTIONS, AND MEANS TO PERMIT GAS UNDER PRESSURE TO BE INTRODUCED IN SAID INFLATABLE MEMBER. 